CASL

Judgement

What it is

Building block

What it does

A JavaScript authorisation library that defines what a user can do with which resources, usable both in the browser and on the server.

Adopt it when

You need the same permission rules in front end and back end of a JavaScript app.

Watch out

Largely one maintainer's project.

Ready for

Production-ready

Runs as

Library

Built with

TypeScript

How established

Established: started 9 years ago, latest release @casl/ability@7.1.1.

What the license allows

You can build it into a product you sell, as long as you keep its copyright notice.

Judged on 2026-11-03 from the project's README and GitHub data. The license and age lines are worked out directly.

Built from

Follow it down: CASL → TypeScript → Go → runs on a microchip

How compilers were built, back to punched paper tape

Open-source alternatives to CASL

1. 1
   Casbin apache

   Apache Casbin: an authorization library that supports access control models like ACL, RBAC, ABAC.

   Building block Production-ready Your application needs configurable permission rules without writing an authorisation engine.

   ★ 20k Apache-2.0 Go Active, pushed today
2. 2
   OPA open-policy-agent

   Open Policy Agent (OPA) is an open source, general-purpose policy engine.

   Building block Production-ready You want one policy language across Kubernetes, CI, APIs and infrastructure, with policies kept outside application code.

   ★ 12k Apache-2.0 Go Active, pushed today
3. 3
   SpiceDB authzed

   Open Source, Google Zanzibar-inspired database for scalably storing and querying fine-grained authorization data

   Building block Production-ready Your app needs fine-grained, relationship-based permissions such as sharing, teams and nested folders across services.

   ★ 7.2k Apache-2.0 Go Active, pushed 5 days ago
4. 4
   OpenFGA openfga

   A high-performance and flexible authorization/permission engine built for developers and inspired by Google Zanzibar.

   Building block Production-ready You need fine-grained permissions as a separate service and want a vendor-neutral, CNCF-governed option.

   ★ 6.1k Apache-2.0 Go Active, pushed 4 days ago
5. 5
   Permify Permify

   An open-source authorization as a service inspired by Google Zanzibar, designed to build and manage fine-grained and scalable authorization systems for any application. — Permify is now part of FusionAuth 🎉

   Building block Usable You want a fine-grained permission service with a readable schema and testing tools.

   ★ 6k AGPL-3.0 Go Active, pushed 11 days ago
6. 6
   Keto ory

   The most scalable and customizable permission server on the market. Fix your slow or broken permission system with Google's proven "Zanzibar" approach. Supports ACL, RBAC, and more. Written in Go, cloud native, headless, API-first. Available as a service on Ory Network and for self-hosters.

   Building block Usable You already use Ory Kratos or Hydra and want permissions from the same stack.

   ★ 5.4k Apache-2.0 Go Active, pushed 2 months ago
7. 7
   Cerbos cerbos

   Cerbos is an open-core authorization management platform for authorizing every identity and governing every action across applications, gateways, workloads, and AI agents.

   Building block Production-ready You want authorization rules out of application code but do not want to sync relationship data into another database.

   ★ 4.6k Apache-2.0 Go Active, pushed 7 days ago
8. 8
   Topaz aserto-dev

   Cloud-native authorization for modern applications and APIs

   Building block Usable You want OPA-based policies plus relationship data in one local authorizer.

   ★ 1.4k Apache-2.0 Go Active, pushed 10 days ago

Commercial authorization and permission engines

1. 1
   Oso Cloud Oso Security

   Oso helps companies run agents in production with confidence using monitoring, access controls, and automated least privilege.

   Building block Usable Your app has outgrown hand-coded role checks and needs relationship- or attribute-based permissions.

   Commercial
2. 2
   AuthZed Cloud AuthZed

   Remove authorization bottlenecks, empower your team to innovate and expand with best-in-class performance at any scale.

   Building block Production-ready A product needs Google Docs-style sharing permissions at scale and the team is ready to adopt a relationship model.

   Commercial
3. 3
   Styra DAS Styra

   Complete system Usable A platform team runs OPA in many places and wants central policy management and impact analysis.

   Commercial